Method and means for surfacing glass



Deqz. 3, 1935. v 5, LONG 2,023275,

METHOD AND MEANS FOR SURFACING GLASS Filed July 28, 1935' INVENTOR Nb 1\ EE/P/VHRD LONG ATTORNEYS Patented Dec. 3, 1935 METHOD AND MEANS. FOR SURFACING GLASS Bernard Long, Paris, France, assignor to Societe Anonyme des Manufactures des Glaces & Produits Chimiques de Saint-Gobain, Chauny &

' Cirey, Paris, France Application July 28, 1933, Serial No. 682,601

In France August 9, 1932 2 Claims.

This invention relates to a method and means for surfacing glass and refers more particularly to a method and means for polishing mirrors and other sheet glass articles.

5 In the course of manufacturing plate glass materials such as mirrors, the surfaces of these materials are usually first subjected to a grinding process and are then polished. The grinding process consists of two steps, the coarse grinding and the fine grinding by emery. The ground surfaces are still comparatively rough after the grinding process has been completed, the unevenness of these surfaces preventing the glass from being transparent. The ground surfaces are 15 then polished and they become quite smooth and even only as a result of this polishing.

The polishing process is also usually divided into two steps, the first one being called the first polishing, or the preliminary polishing, while the second step is called the finishing, or the final polishing.

In the course of the first polishing the small projections formed on the surface of the glass are. removed with the result that the glass becomes transparent, although the visible cavities and grooves are removed only at the end of the.

- final polishing.

In prior art both the preliminary polishing and the final polishing were carried out by polishing blocks which were moved over the surface of the glass. These polishing blocks have surfaces consisting of felt, cloth or even bituminous substances, such as pitch, for instance, mineral pitch, which carry abrasives, such as metallic oxides, for instance iron oxide and aluminium oxide. It was found, however, that the polishing by these blocks requires a considerable amount of time; it seldom takes less than three quarters of an hour, and in most cases it has to be continued for more than one hour. The polishing surfaces made of felt must have a certain amount of moisture and the quality of the work depends largely on the amount of moisture used. However, it is quite diflicult in the course of the polishing process to maintain the same amount of moisture in the felt with the result that usually the felt, when it is passed over one particular part of the glass surface, has much more moisture than it has when another part of the glass sur- 50 face is being treated. These differences in the amount of moisture cause a considerable variation in the length of time required for the Work, in the quality of the finished article and in the amount of energy, which has to be expended.

An object of this invention is to provide a method and means for polishing glass articles, by which the polishing operation may be completed in a relatively short time.

A further object is the provision of a device with which the regulation of the amount of 5 moisture contained in the polishing surface is much easier."

The above and other objects of this invention may be realized through the use of a method of brushing the glass surface by brushes made of a not readily corrodible metal. The bristles of these brushes consist, preferably, of brass and are very thin and pliable, the diameter of the bristles being about 8/100 to 10/100 of a millimeter. The ends of the bristles areimmersed into a mixture of water and metallic oxides, such as iron oxide, and are then moved over the surface of the glass. This method of brushing the glass surfaces is also, preferably, divided into two steps, namely the first or preliminary brushing and the second or final brushing; it is used in combination with the grinding process and is applied after the grinding has been completed.

The invention will appear more clearly from the following detailed description when taken in connection with the accompanying drawing showing a preferred embodiment of the inventive idea.

The drawing is a partial side view and vertical section of a brush applied to the surface of a glass article.

The brush illustrated in the drawing consists of parallel metallic holders I and thin metallic bristles 2, which are firmly connected with the holders 1. The holders are fastened by bolts 3 to a circular plate 4 which is driven by a rotating shaft 5. The bristles 2 are made of a not readily corrodible metal, such as brass. The free ends 6 of the bristles 2 carry a mixture I, which consists of water and one or more oxides, for instance 40 iron oxide. The ends 6 of the metallic bristles 2 are moved by means of the plate 4 over the surface 8 of the glass sheet 9, which is carried by a support Ill. The brush is passed over the sheet 9 until the surface 8 of the sheet is made com pletely smooth and even.

The use of such metallic brushes is extremely advantageous since the time necessary for the first or preliminary brushing of a glass surface is only from live to ten minutes. The final or sec- 0nd polishing does not require more than twenty or thirty minutes.

A further advantage of these brushes is that it is easy to clean them since the water and the oxides penetrate very readily into the spaces 'between the thin bristles and can be quickly removed from them whenever necessary.

- Another advantage of this new method is that the surface of the brush has the same amount of moisture during the entire brushing process.

One of the most important advantages is the easiness with which the brushes may be moved over the surface of the glass. The amount of energy per unit of area, which is necessary for brushing a glass surface, varies merely with the variation of the pressure exerted by the brushes and with the speed with which they are moved over the glass surface. If the amount of pressure and the speed remain the same, the amount of expended energy will also remain constant to a remarkable extent.

The brushing of the glass surfaces may be used as a substitute for both the first or preliminary polishing and for the final or second polishing. In the-course of the first brushing the pressure which the brush exerts on the glass surface should be about 2 kgs. per sq. dcm.; the speed with which the brush is moved with respect to the glass may vary from 2 to 5 meters per second.

The second brushing, used as a substitute for the final polishing, is carried out at a pressure of about 1 kg. per sq..dcm. On the other hand the velocity with which the brush is moved with respect to the glass surface is doubled and may reach as much as meters per second.

The above figures are given by way of example and can vary to a large extent depending on the nature of the glass and on the material out of which the metal brushes are manufactured.

The brushing method, which forms the subject-matter of the present invention, may be used in combination with the usual polishing method, in the course of which a polishing surface consisting of felt and pitch is used. This combined brushing and polishing method is applied when the original grinding process was not successful so that the ground surface remains very rough and uneven. The first step of the combined brushing and polishing process consists in surfacing the glass by means of brushes provided with metal bristles. The second. step comprises the use of polishing surfaces made of felt carry- 5 ing metallic oxides.

What is claimed is:

1. The method of polishing a glass surface, which comprises brushing the same with metallic bristles and a mixture of water and an abrasive 10 carried by the ends of said bristles by causing a relative movement between said bristles and the glass surface while the ends of said bristles are maintained in contact with the glass surface during the entire polishing and are pressed against the glass surface with a force which is independent of the velocity of the relative movement between the bristles and the glass surface, whereby a uniform and simultaneous action of the metallic bristles and the abrasive upon the treated glass surface is assured.

v2. Means for surfacing glass, comprising a plurality of metallic bristles, each of said bristles having a diameter ranging between five hundredths and fifteen hundredths of a millimeter, a mixture of water and an abrasive carried by the ends of said bristles, a support adapted to carry the glass surface to be treated, a plate extending substantially parallel to said glass surface, means for attaching said metallic bristles to said plate, and means connected with said plate for rotating the same around a central axis which is substantially perpendicular to said glass surface and which extends in substantially the same direction as that of said bristles, the last-mentioned means maintaining the ends of said bristles incontact with the glass surface during the entire polishing and pressing them against said glass surface with a force which is independent of the velocity of the movement of said bristles in re- .lation to the glass surface.

BERNARD DONG. 

